This invention relates to an intumescent fire retardant material, and particularly a material which has the ability to remain in the flexible unexpanded form, until heat, such as that produced by a fire, is applied, at which time it will expand to become a substantially rigid refractory thermal insulator.
Industry has long sought better materials to effectively fill voids left by burning or melting cable insulation as in the case of a fire in modern office buildings. Better thermal insulating coverings for walls, doors, ceilings, etc., are also needed. The materials heretofore employed provided protection for only limited periods because of poor stability at elevated temperatures or damage by high-pressure water sprays due to low mechanical strength. They have had the further disadvantage that they were not waterproof and had low volume expansions and pressure generation, particularly at low temperatures, with a resultant loss in their capacity to fill void areas or provide thermal insulation, thus allowing the spread of smoke or fire.
U.S. Pat. No. 3,786,604 is illustrative of the prior art and discloses the concept of filling the gap between a concrete floor slab and an upright curtain wall with a urea formaldehyde resin foam which is supported in a trough made of thin resilient sheet steel. The steel trough support is required because the mechanical strength of the foam is relatively low and that of the charred foam is even lower.
U.S. Pat. No. 3,429,836 discloses a process for producing thermal insulating coverings from organic (polystyrene and copolymers of styrene) foam materials in combination with alkali metal silicates. The composition is made into rigid boards for use as thermal insulating covers on surfaces such as walls, ceilings, doors, and the like. The formed board-like material must be coated with a protective layer of lacquers or plastic films to render it moisture resistant.
U.S. Pat. No. 3,983,082 relates to a silicone resin base fire retardant system having a temperature capability to at least about 230.degree. C. and combines intumescent characteristics with a crusting and charring capability. These materials are intended primarily for use in aircraft gas turbine engines and they are most effective at relatively high temperatures on the order of 1000.degree. C. or higher.